The Cycling Thread

[maviczap]

Off to London bike show tomorrow

[fizzwheel]

Originally Posted by maviczap

Off to London bike show tomorrow

Enjoy

[maviczap]

Better leave the credit card at home

[carelesschucca]

wheres the fun in that?

[maviczap]

Originally Posted by carelesschucca

wheres the fun in that?

I didn't say i wouldn't be getting anything, im just going to "aquire" it. Amazing how much you can get in a blue Ikea bag

Originally Posted by Adam Ef

Weight saving on rims and tyres is good. When spinning it accounts for more than the actual weight saving due to rotating mass / centrifugal force being lighter. Saving 250g in rims / tyres is actually equivalent of saving something like 1000g for the energy you need to move forwards when up to a certain speed, about 20 to 30mph I think.

That old chestnut...

Rotational inertia...

Steady state... all else (frictional losses, aero, rolling resistance etc) equal light wheels require the same power to turn at a constant speed.

Acceleration... all else equal, lighter wheels require less power to accelerate.

Climbing is where the latter is felt the most... if the rider isn't smooth on the delivery climbing can become a series of micro accelerations which sucks up a lot of power. Speed ripple might only be a few cm/s (bike computers don't have the resolution to measure this), but it is a lot when it is happening 180+ times per minute and on each pedal stroke the rider is having to put back the energy into rotating masses (there's a squared relationship in there) (plus forward energy) lost on the last that could well be the equivalent of pushing a handful of extra kilos up a hill... certainly more than just lifting the 200-400g difference in wheel weight.
Light wheels or a very smooth delivery or both win... bottom line, it is the rider who is the culprit. It is something to work on even though the ripple will never be completely eliminated.

The same micro accelerations apply on the flat btw, however the effect is far less pronounced than when working against gravity.

So yes and no, but not quite what you said... Lighter wheels only have an advantage accelerating which might be happening more frequently than people realise.

[Adam Ef]

But now we know that gravity works in waves.. I'm working on a new hill climb technique only putting the effort in inbetween the waves when it will have the most effect. : )

[Adam Ef]

All riding is kind of acceleration though too, in as much as if you don't pedal then you slow and stop, so you're always trying to counteract that stopping effect, just not an acceleration from zero.

I definitely notice the effect of heavier tyres on 29er mountain bike.. same size wheels in theory as my road bike and rim weight is similar but requires much more to keep it going and get up to speed, and loads harder to climb with. Having said that the momentum of the heavy rubber when up to speed probably helps keep it rolling a fair bit on the flat, compared to 26" mountain bike which seems to stop dead if there's no pedalling.

[carelesschucca]

We could be slightly less obsessive and just get out and ride...



Says the boy that's champing at the bit to get home and look at his brand new carbon framed toy...

Dean, it is all aimed at greater efficiency.